1. Field of the Invention
The present invention relates to a method for coating with a coating liquid using a die, a coating apparatus for use therein and a method for designing the same and, more particularly, relates to a method for uniformly coating without inducing coating stripes, a coating apparatus for use therein and a method for designing the same.
2. Description of Related Art
Conventionally, designing of the insides of slot dies has been conducted in such a way as to uniformize the amount of a coating liquid ejected from a die ejecting portion in the direction of the width, in order to suppress the variation of the coating thickness in the direction of the width for improving the uniformity of the coating thickness. A slot die is provided with a slot (manifold) for transferring a coating liquid to the inside of the die in the direction of the width and a slit-shaped flow channel for offering the effect of rectifying the coating liquid between the manifold and the die ejecting portion. Accordingly, the shape of the manifold, particularly the cross-sectional shape thereof in the direction of flow of the coating liquid, is designed, in such a way as to uniformize the pressure loss caused between the manifold and the ejecting portion in the direction of the width or in such a way as to uniformize the cross-sectional area of the manifold in the direction of flow of the coating liquid, in order to uniformize the amount of the coating liquid ejected in the direction of the width (refer to Japanese Unexamined Patent Publication No. 5-50004).
However, with a slot die produced according to the design, the flow rate of the coating liquid is decreased within the manifold as the coating liquid flows away from a liquid supplying portion which supplies the coating liquid to the manifold, which increases, at an accelerated pace, the time period during which the coating liquid flows within the die as the coating liquid approaches the coating end. This induces the problem of degradation of the external appearance of the coating film, such as the occurrence of stripes, in cases of using a time-varying coating liquid, such as slurry containing dispersed particles, with the slot die produced according to the design.